Inner tube for pneumatic tires



March 14, 1939. V. E. EGER INNER TUBE FOR PNEUMAT IC TIRES Filed July 12, 1935 INVENTOR.

ERNST @GER 's fir.

ATTORNEY AND WHEELS Patented Mar. 14, 1939 UNITED STATES Search Roon PATENT OFFICE INNER TUBE FOBPNEUMATlC TIRES Ernst Eger, Grosse Pointe Park, Mich., assignor,

by mesne assignments, to United States Rubber Company, New York, N. Y., a corporation of New Jersey Application July 12, 1935, Serial No. 30,978

1 Claim.

My invention relates to safety inner tubes used in pneumatic tires, particularly automobile tires. More particularly, the invention relates to inner tubes having a plurality of inflatable compartments.

Due to the present large cross sectional sizes of pneumatic tires and the increased speeds of automotive vehicles, considerable danger is involved due to the possibility of a tire becoming suddenly deflated. It is, therefore, an object of my invention to provide an improved construction in safety tubes wherein if one tube becomes deflated a sec'- ond tube takes its place, thus preventing a sudden and total deation of the fluid pressure carrying medium within the casing.

In the inner tube of my construction, the rim engaging or inner chamber is a complete unit having its outer peripheral surface less yieldable than its inner rim engaging surface; and the outer chamber is mounted over the crown portion of the inner chamber and is more yieldable than the inner chamber so that the stiffer wall of the inner chamber acts to control the distribution of fluid pressure between the chambers. Preferably, the yielding characteristics of the chambers are controlled by the thicknesses of the rubber used.

These and other objects and advantages appear more fully in the following detailed description when considered in connection with the accompanying drawing, in which:

Fig. lis a transverse view in section of an inner tube embodying my invention;

Fig. 2 is a transverse view in section of a portion of the valve mechanism;

Fig. 3 is a transverse view, in section, of a tube of my invention, in normal operative assembly with a pneumatic tire and rim; and

Fig. 4 is a similar view illustrating the outer chamber in deflated condition.

Referring to Fig. l, there is shown an embodiment of my invention in the form of a safety tube having independent air chambers I and 2. 'I'he inner chamber I is formed by an annular tube of rubber 3 somewhat similar to the conventional inner tube. The outer chamber 2 is formed in part by the outer periphery of the tube 3, and in part by a circumferential strip of rubber 4 extending around the tube 3 and attached thereto at seams near the rim portion of the tube. The strip of rubber 4 is secured to the tube 3 by a vulcanizing operation or by cementing the strip in place,.as hereinafter described.

Associated with the tube 3 is a valve stem 5 which may be secured to the tube 3 by mechanical means such as a conventional all-metal valve stem, or by a part rubber assembly such as a pad 6, shown in the drawing.

My safety tube requires a special valve connection so that fluid under pressure may simultaneously pass into each of the chambers I and 2 through independent connections.

Within the valve stem 5 is a conventional valve core 1. This core operates alone to seal the fluid pressure within the air chamber 2. In the initial ination of the chamber 2, the fluid under pressure passes fromA a conventional air chuck (not shown) into an aperture 8 of the valve stem 5 and follows through an aperture 9 of an extension I0 of the valve stem 5. This is shown in detail in Fig. 2.

Associated with the extension I0 is a exible hose II which connects the aperture 9 with the air chamber 2. A patch I2 forming a part of the rubber hose I I is secured to the tube 3 at the crown portion of the outer periphery of the tube 3. Thus, a direct independent passageway is formed from the aperture 8 of the valve stem 5 to the chamber 2 through the chamber I.

Within the chamber I and secured to the inner end of the valve stem 5 is a valve mechanism retainer I3 containing a Valve core I4. This places the valve core I and the core I4 in direct axial alignment. A plunger pin I5 is disposed within the aperture 8 of the valve stem 5, and functions as an extension of the pin which forms a part of the Valve core 1 so that actuation of the pin in the valve core I mechanically produces a corresponding actuation of the valve core I4. When the valve core I4 is open, a communication is formed between the aperture B within the valve stem 5 and the chamber -I.

From the foregoing it is apparent that the application of a conventional air chuck at the outer end of the valve stem 5 will function to introduce uid under pressure into the aperture 8 through the valve core I4, and into the chamber I; and,

in addition, will permit a free flow of uid under y pressure from the aperture 8 through the aperture 9 and hose connection II into the chamber 2. Accordingly, by this form of valve mechanism the chambers I and 2 may be inflated simultaneously, while at the same time the fluid pressure is retained Within the respective chambers by independent means. However, when it is desired to deflate the safety tube an operator may, by depressing the plunger in the valve core lI, also cause the plunger within the valve core I4 to -be depressed, thus releasing the uid pressure from the chambers I and 2 simultaneously.

In order to obtain the proper functioning of my safety tube I find it desirable to use diiIerential thicknesses for the walls which form the chambers I and 2. For example, and not as a limitation of the invention, I nd it preferable to maintain the thickness of the wall of the tube 3, particularly at the crown portion thereof, at a gauge of approximately .200 inch. However, the

thickness of the wall of the tube 3 at the base or rim portion may be reduced to a gauge thickness of .125 inch. This reduction in the thickness of the wall at the base of the tube is preferable V with a penumatic tire I6 and rim I1. When my safety tube is mounted within the tire I6 and inflated, the fluid pressure passes into chambers I and 2 simultaneously. During this inflation process both'chambers I and 2 directly communicate with the aperture 8 of the valve stem 5. Accordingly, any resistance by either of the chambers to the free flow of iiuid pressure will operate'to increase theiiow of fluid pressure to the other chamber. At a denite stage in the ilow of fluid pressure into the chambers I and 2, the wall of the tube 3, because of its thickness, will resist expansion until the thinner wall 4 of the chamber 2 has reached the point of inextensibility due to its confinement by the tire casing I6. Thereafter the tube 3 will remain in a neutral position such as shown in Fig. 3 by reason of the balanced fluid pressures within the respective chambers. f

In Fig. 4, chamber 2 is shown in a deflated condition, as by being punctured or otherwise relieved of its fluid pressure retaining capacity. In such case the tube 3 expands` and assumes a. position occupying the entire area within the tire casing. It has been demonstrated that a fluid pressure of thirty-two pounds within the chambers I and 2 will,upon deflation of the chamber 2, result in a remaining' pressure of nineteen pounds within the chamber I. Such a reduction in pressure normally is not excessive to a point in which the tire casing will incur serious damage. In order to attain the advantages of my invention it is essential that the cross sectional area of the tube defined by the wall 3 should equal at least 50 per cent of the total cross sectional area of the combimed chambers I and 2.

It is also understood that the cause which produces deflation of the chamber 2 may persist and also produce deflation of the chamber i. The cause which produces deflation of the chamber 2 would not under ordinary circumstances operate instantly to produce deflation of the chamber I.

v Thus, the operator of a vehicle having inner tubes of my embodiment would, after the first tube becomes deflated, become sufficiently apprised of the occurrence by reason of the swaying or riding quality of the vehicle due to this partial deflation. `With this knowledge the operator may gradually bring the vehicle to a stop without endangering the stabiliity of the vehicle, and without danger to the tire casing. 4It has also been found that the vehicle may be driven many miles after the partial deiiation, without serious injury t0 the tire carcass as the tube 3 expands to fill the tire cavity, as shown in Fig. 4, therebyy directly supporting the tire plies.

In some cases, where the secondary tube is not extensible, and does not fill thev tire cavity, detrimental results follow when the secondary tube is in operation, by reason of the friction due to the difference between the circumferential length of the crown portion of the secondary tube, and the peripheral length of the interior of the tire at the crown thereof. My invention, therefore, is advantageous in that the secondary tube or tube 3 expands and functions as a conventional tube without friction between the outer periphery of the tube and its adjacent engaging surface of the tire. If desired, the rubber strip 4 may be provided with ribs I8 deiining venting passageways I9 for engaging the inner peripheral wall of the tire I6.

The first step in the manufacture of my dual tube isthe tubing of the inner inner-tube 3. This is accomplished in the usual manner; that is, the ends of the tube are buffed'and spliced together to form an annular member. A hole is cut in the top of the tube opposite the valve mechanism, and the hose il and pad I2 forming an integral part thereof, is assembled with the tube. Usually a bufng on the tube in the area of the pad is required before the pad is stitched in position on the tube. The opposite end of the hose II is closed temporarily such as by pressing a wooden pin into the open aperture. Next a temporary valve stem, such as an ordinary bicycle valve stem, is applied to the valve region of the inner tube 3. In this condition the inner tube 3 is placed in a heater and vulcanized. During vulcanization the hose II performs no operation, but merely hangs loosely within the inner tube 3.

The wall of the outer chamber 2 is originally tubed in the form of a continuous strip of tubing. A measured length of this tubing is slit longitudinally and its ends are spliced together to form, in effect, a band. The vulcanized inner tube 3 is buffed on its outer periphery in a circumferential path at which it is intended to secure the ends of the band of rubber I. A coating of cement is applied on the circumferential, buffed path and allowed to dry, after which the ends of the strip of rubber are stitched along a definitely marked location.

Before the strip of rubber 4 is secured to the inner tube, the contacting area of the strip of rubberl 4 is also bued. At this step of the manufacture of the tube the temporary bicycle valve stem previously vulcanized to the inner tube is cut away from the tube I3, and the valve stem region is buifed and cemented. The hose II is partialhr withdrawn from within the inner tube 3 through the valve stem aperture, the wooden pin is removed, -and the hose is attached to a completely assembled valve mechanism. The pad 6 attached to the valve stem is stitched in place on to the inner tube 3, and the entire assembly is again placed in a heater of larger dimensions and vulcanized. I

During the second vulcanizing operation the inner tube 3 expands to a point of equilibrium, while the outer wall f3 conforms tc the profile of the mold. By this method the inner tube is subjected to a double Vuicanizing oration, which apparently results in no ill effect.

While I have shown and described a present preferred form of the invention, it is to be understood that the invention may be otherwise em= Home bodied within the spirit oi the invention and the scope of the appended claim.

Having thus described my invention what I claim and desire to protect by Letters Patent is:

A multi-chamber inner tube comprising a rubber inner tube the wall thickness of which increases progressively youtwardly from its inner periphery towards its outer periphery, an outer rubber envelope attached only at its edges to the 10 side walls of ythe inner tube and above the rim engaging portion of the tube to form a second air chamber, the rubber oi' the envelope 'being more yielding than the rubber of the enclosed portion of: the inner tube whereby the envelope expands under internal pressure more readily than the inner tube, and means for simultaneously inflating said tube and chamber with iiuid from a lcommon source to obtain a. balanced pressure therein.

ERNST EGER. 

